Search

A) CT and MRI of patient with prolonged partial response with MTL-CEBPA treatment B) IFN-gamma, NFkB and IL6 trend at days 1, 8 and 15 following treatment and C) AFP change at from baseline to 4, 8 and 16 weeks on treatment

Supplementary Legends

Showing complete radiological response of lung metastases

Dose escalation flow chart. DLT - dose limiting toxicity, MTD - maximum tolerated dose

Trial Protocol

Supplementary Table 1 CEBPA-51 PK parameters Supplementary Table 2 RECIST 1.1 response observed overall and per cohorts in HCC patients at cut-off (12 Sep 2018) presented as n (%)

Purpose:Transcription factor C/EBP-α (CCAAT/enhancer-binding protein alpha) acts as a master regulator of hepatic and myeloid functions and multiple oncogenic processes. MTL-CEBPA is a first-in-class small activating RNA oligonucleotide drug that upregulates C/EBP-α.Patients and Methods:We conducted a phase I, open-label, dose-escalation trial of MTL-CEBPA in adults with advanced hepatocellular carcinoma (HCC) with cirrhosis, or resulting from nonalcoholic steatohepatitis or with liver metastases. Patients received intravenous MTL-CEBPA once a week for 3 weeks followed by a rest period of 1 week per treatment cycle in the dose-escalation phase (3+3 design).Results:Thirty-eight participants have been treated across six dose levels (28–160 mg/m2) and three dosing schedules. Thirty-four patients were evaluable for safety endpoints at 28 days. MTL-CEBPA treatment–related adverse events were not associated with dose, and no maximum dose was reached across the three schedules evaluated. Grade 3 treatment-related adverse events occurred in nine (24%) patients. In 24 patients with HCC evaluable for efficacy, an objective tumor response was achieved in one patient [4%; partial response (PR) for over 2 years] and stable disease (SD) in 12 (50%). After discontinuation of MTL-CEBPA, seven patients were treated with tyrosine kinase inhibitors (TKIs); three patients had a complete response with one further PR and two with SD.Conclusions:MTL-CEBPA is the first saRNA in clinical trials and demonstrates an acceptable safety profile and potential synergistic efficacy with TKIs in HCC. These encouraging phase I data validate targeting of C/EBP-α and have prompted MTL-CEBPA + sorafenib combination studies in HCC.

Longitudinal changes in WBC mRNA expression of CEBPA, adenosine, PD-1 & CXCR4 at screening, day2, 8 and 15 of a single patient treated in the 130mg/m2 cohort

qPCR of CEBPA mRNA levels at days 2, 8 and 15 following treatment

Despite significant advances in outcomes with immunotherapy, most cancer patients do not benefit from currently approved immune checkpoint inhibitors (ICI). The reasons for ICI resistance are multi-faceted and suggest that additional immunomodulation is required to improve outcomes. MTL-CEBPA is a novel immunotherapy based on RNA activation that upregulates expression of a master myeloid transcription factor, CEBPA. The small activating RNA for CEBPA is encapsulated within a NOV340 liposome that targets the myeloid cell lineage. MTL-CEBPA has shown favorable safety and promising clinical activity in combination with tyrosine kinase inhibitors (Sorafenib) in hepatocellular carcinoma (NCT-02716012) [Hashimoto et al, CCR 2021; Sarker et al, CCR 2020]. We recently reported preliminary clinical data from the ongoing multi-center phase 1 TIMEPOINT study (NCT-04105335) evaluating the safety, pharmacokinetics, immunomodulation, and clinical activity of MTL-CEBPA in combination with pembrolizumab in patients with solid tumors who have exhausted standard therapy. This demonstrated a favorable safety profile and initial clinical activity [Plummer et al, JITC 2021]. Here we report the findings from a biomarker pharmacodynamic analysis of paired baseline and cycle 2 tumor sample biopsies in 23 patients from the TIMEPOINT trial. Brightplex® IHC and digital pathology analyses of the samples for myeloid and T cell panels were undertaken, alongside gene expression (Nanostring I/O 360). Prior to study treatment, nine patients out of 23 had an immune cold tumor microenvironment (TME) at baseline as measured by the Immunosign®21 score. Following the combination of MTL-CEBPA with pembrolizumab, seven of these patients converted to an inflamed TME by Immunosign®21 (P=0.008). This change in the TME was associated with infiltration of CD8 and cytotoxic T cells (CD8+, GrzB+, Ki-67+) (P=0.1). GSEA analysis indicated that a Tstem-like signature was enriched post-treatment. A Brightplex® IHC analysis of myeloid cells in these patients indicated that, post treatment, there was a significant influx of HLA-DR+ myeloid cells into the TME (P=0.04). We also observed a significant increase in the expression of CXCL9, 10, and 11. The remaining 14 patients had an inflamed TME at baseline. Here, we also observed an increase in HLA-DR+ cells, T cells, and chemokines, though to a lesser extent. Further, however, in these inflamed tumors—which have significantly greater infiltration of myeloid-derived suppressor cells (MDSCs) than desert tumors—we observed a reduction in 8/10 patients with detectable PMN-MDSCs (P=0.1) post treatment, consistent with the mechanism of action of CEBPA. An expression signature based on 18 genes significantly enriched for clinical response across all patients. Collectively, these data suggest a positive immunomodulatory TME effect of the combination of MTL-CEBPA with pembrolizumab. In both hot and cold TME tumors, the combination drives directed differentiation of progenitor monocytes into HLA-DR+ myeloid cells secreting chemokines that stimulate the ingress of T cells into the TME. We observe a significant positive correlation between the change in cytotoxic T cells and HLA-DR+ myeloid cells post treatment (P=0.004). These effects are most pronounced in cold tumors. Citation Format: Ruth Plummer, Mikael Sodergren, Brid Ryan, Ilian Tchakov, Nina Raulf, Rose Hodgson, CP Tan, Joanna P. Nicholls, Alison Adderkin, N Vasileiadou, Vikash Reebye, Tim Meyer, David J. Pinato, Debashis Sarker, Bristi Basu, Sarah Blagden, Natalie Cook, Jeff Evans, Jeffrey Yachnin, Cheng Ean Chee, Dan Li, Anthony El-Khoueiry, Maria Diab, Kai-Wen Huang, Marcus S. Noel, Bridget Keenan, Devalingam Mahalingam, Melanie Grosso, Denis Arnaud, Aurelie Auguste, Jan Storkholm, Iain McNeish, Robert Habib, John J. Rossi, Nagy Habib. MTL-CEBPA in combination with pembrolizumab converts an immune desert to an inflamed TME in solid tumors resistant to checkpoint blockade [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB192.

Purpose: To evaluate the mechanisms of how therapeutic upregulation of the transcription factor, CCAAT/enhancer-binding protein alpha (C/EBPα), prevents tumor progression in patients with advanced hepatocellular carcinoma (HCC) and in different mouse tumor models. Experimental Design: We conducted a phase I trial in 36 patients with HCC (NCT02716012) who received sorafenib as part of their standard care, and were given therapeutic C/EBPα small activating RNA (saRNA; MTL-CEBPA) as either neoadjuvant or adjuvant treatment. In the preclinical setting, the effects of MTL-CEBPA were assessed in several mouse models, including BNL-1ME liver cancer, Lewis lung carcinoma (LLC), and colon adenocarcinoma (MC38). Results: MTL-CEBPA treatment caused radiologic regression of tumors in 26.7% of HCC patients with an underlying viral etiology with 3 complete responders. MTL-CEBPA treatment in those patients caused a marked decrease in peripheral blood monocytic myeloid-derived suppressor cell (M-MDSC) numbers and an overall reduction in the numbers of protumoral M2 tumor-associated macrophages (TAM). Gene and protein analysis of patient leukocytes following treatment showed CEBPA activation affected regulation of factors involved in immune-suppressive activity. To corroborate this observation, treatment of all the mouse tumor models with MTL-CEBPA led to a reversal in the suppressive activity of M-MDSCs and TAMs, but not polymorphonuclear MDSCs (PMN-MDSC). The antitumor effects of MTL-CEBPA in these tumor models showed dependency on T cells. This was accentuated when MTL-CEBPA was combined with checkpoint inhibitors or with PMN-MDSC–targeted immunotherapy. Conclusions: This report demonstrates that therapeutic upregulation of the transcription factor C/EBPα causes inactivation of immune-suppressive myeloid cells with potent antitumor responses across different tumor models and in cancer patients. MTL-CEBPA is currently being investigated in combination with pembrolizumab in a phase I/Ib multicenter clinical study (NCT04105335).

Tumor associated macrophages (TAM) and myeloid-derived suppressor cells (MDSC) are widely implicated in the suppression of immune responses in cancer and are associated with negative clinical outcomes. We report that in mouse tumor models, therapeutic up-regulation of the transcriptional factor C/EBPα with small activating RNA (MTL-CEBPA) blocks the suppressive activity of monocytic (M) MDSC and TAM without affecting polymorphonuclear (PMN) MDSC. MTL-CEBPA treatment demonstrated antitumor activity that was dependent on T cells. Combination of MTL-CEBPA and anti-PD1 antibody or with PMN-MDSC targeted therapy resulted in marked antitumor effect. A phase I trial was conducted in 36 patients with advanced hepatocellular carcinoma (HCC). Marked decrease in M-MDSC and the expression of genes and proteins involved in immune suppressive activity of these cells were observed. Combined treatment with MTL-CEBPA and sorafenib resulted in a 27% objective radiological response and three complete responses in patients with virally associated HCC. Tissue biopsies from these patients demonstrated decrease in M2 polarized macrophages within the tumors. Thus, therapeutic up-regulation of C/EBPα inhibited suppressive myeloid cells that resulted in potent antitumor effect in mice and with encouraging clinical response in cancer patients. We are currently recruiting to a multi-centre study of MTL-CEBPA in combination with a PD-1 inhibitor (pembrolizumab) in adult patients with advanced solid tumors (TIMEPOINT - ClinicalTrials.gov Identifier: NCT04105335). Citation Format: Ayumi Hashimoto, Debashis Sarker, Vikash Reebye, Sheba Jarvis, Mikael H. Sodergren, Andrew Kossenkov, Nina Raulf, Jenni Vasara, Pinelopi Andrikakou, Tim Meyer, Kai-Wen Huang, Ruth Plummer, Cheng Ean Chee, Duncan Spalding, Madhava Pai, David J. Pinato, Rohini Sharma, Bristi Basu, Daniel Palmer, Yuk-Ting Ma, Robert Habib, Anna Martirosyan, Naouel Elasri, Adeline Reynaud, John Rossi, Mark Cobbold, Nagy Habib, Dmitry Gabrilovich. Up-regulation of C/EBPα inhibits suppressive activity of myeloid cells and potentiates antitumor response in mice and cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1730.

MTLCEBPA, a non-toxic therapeutic oligonucleotide formulated inside SMARTICLES (liposomal nanoparticles) is currently under a Phase I study for patients with advanced hepatocellular carcinoma (HCC). We have demonstrated in multiple in vivo liver disease models that MTLCEBPA can improve liver function and inhibit HCC tumor growth. Here we show that upregulation of hepatic CEBPA expression by MTLCEBPA enhances the effects of Sorafenib in a (Diethylnitrosamine) DEN induced cirrhotic HCC rat model by significantly reducing liver tumor volume after only two weeks of combination treatment when compared to untreated control or single agent treatment only. In this study, we established cirrhosis and HCC by exposing male Wistar rats to DEN for 6 weeks. Animals were randomized into 5 groups comprising of: 1. PBS control; 2. MTL-CEBPA treatment (TIW at 3mg/kg) for one week; 3. MTL-CEBPA treatment (TIW at 3mg/kg) for two weeks; 4. Sorafenib TIW at 10mg/kg for two weeks; and 5. MTLCEBPA at 3mg/kg at week one combined with Sorafenib 10mg/kg at week 2 group. The results here indicate that Sorafenib combined with MTLCEBPA significantly inhibits tumor growth when compared to single agent treatment. Tumor sizes averaged at 644.7mm3 (± 88.57) in group 1 compared to 326mm3 (± 53.05) in group 2; 199.7mm3 (± 54.73) in group 3 and 299.5mm3 (± 77.1) in group 4. In combination treatment (group 5) the tumor sizes averaged at 101.3mm3 (± 37.48). Serum AFP change (posttreatment values - pre-treatment) was more prominent in the MTLCEBPA/Sorafenib combination treatment (group 5) where there was a 4-fold reduction in values after treatment when compared to control groups 1-4. Serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) and total bilirubin remained unchanged across all the treatment groups suggesting no deterioration in liver function during the study period. These results suggest that MTLCEBPA improved the efficacy of Sorafenib in this DEN induced HCC model, indicating a promising therapeutic option for advanced HCC patients who can no longer be treated with potentially more effective local therapies. Citation Format: Nagy A. Habib, Kai-Wen Huang, Vikash Reebye, Mikael Sodergren, John Rossi. MTLCEBPA, a drug candidate for hepatocellular-carcinoma enhances efficacy of Sorafenib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3856.

The transcription factor CEBPA (CCAAT/enhancer-binding protein alpha) is recognised for its antiproliferative effects. MTL-CEBPA is a small activating RNA drug which upregulates gene expression of CEBPA and amongst other effects causes and immunomodulatory effect on peripheral granulocytes. Radiofrequency ablation (RFA) is standard treatment for some tumour types such as liver cancer and induces modulation of both innate and adaptive immune systems. To investigate any synergistic effect of MTL-CEBPA with RFA and immune checkpoint inhibition we initiated a reverse translation experiment, where syngeneic BNL hepatocellular carcinoma tumour cells were injected in the two opposite flanks of immunocompetent BALB/c mice (n=8 in each group). Treatments for hepatoma bearing mice included: 1) RFA on one flank (day 0), 2) Anti-PD-1 inhibition immunotherapy (RMP1-14 antibody, BioXCell, West Lebanon, NH, USA at 200 μg IV/mouse/dose on days 0, 2 & 5) and 3) MTL-CEBPA (3mg/kg IV/mouse/dose on days 0, 2 & 5) as well as combinations of all 3 interventions. We found that tumour control on the opposite flank was augmented by addition of RFA and most significant in the triple combination group (RFA + anti-PD1 + MTL-CEBPA) in which 2/8 animals showed a complete response and 5/8 a partial response. This was also the only group that showed a statistically significant increase in CD8+ (Cytotoxic) as well as CD49b+/CD45+ (Natural Killer) tumour infiltrating lymphocytes. These data suggest a clinical role for combination treatment with checkpoint blockade, RFA and MTL-CEBPA through synergistic priming of the immune tumour response, enabling RFA to have a pronounced anti-tumour abscopal effect. Citation Format: Mikael H. Sodergren, Kai-Wen Huang, Vikash Reebye, Cheng-Ean Chee, Dimitris Zacharoulis, Robert Habib, David Blakey, John Rossi, Nagy Habib. MTL-CEBPA combined with radiofrequency ablation and immunotherapy enhances immunological anti-tumour response in an HCC mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3211.

CCATT/enhancer binding protein alpha (CEBPA) is a transcription factor that can act as a tumor suppressor. Its expression is downregulated in a number of cancers including hepatocellular carcinoma (HCC). We have investigated the role of CEBPA in models of HCC using small activating RNAs (saRNA) to transcriptionally upregulate its expression. Three liver tumor cell lines (HepG2, Hep3B, PLCPRF5) were transfected with 20nM CEBPA-saRNAs (CEBPA51). The transcriptional regulation of two key members of the CEBP family: CEBPA and CEBPB and their protein expression level were measured. The impact on cell growth was assessed by way of an SRB and WST-1 assay. To investigate the role of CEBPB in protecting cells from the activity of CEBPA, siRNAs were used to knock down CEBPB. Using i.v. delivery of CEBPA51 oligonucleotide, the impact on tumor growth was investigated in a DEN (N-nitrosodiethylamine) model of liver cancer. Rats were treated with DEN for 7 weeks, followed by a 2 week wash out and then treated with the CEBPA51 (3-4mg/kg) complexed with PAMAM-dendrimers or encapsulated in a nanoparticle formulation (SMARTCLES). The impact on CEBPA mRNA levels in the liver, tumor growth and liver functions (including, bilirubin, ALT and AST) were measured. Transfection of CEBPA51 into HepG2, Hep3B or PLCPRF5 cells after 72hr led to a significant increase in both CEBPA mRNA (1.7-2.5 fold by qPCR) and protein expression measured by western blot in all 3 cell lines. A significant inhibition in cell growth compared to either PBS or control oligonucleotide was observed in HepG2 and Hep3B but not in PLCPRF5 cells measured by both SRB and WST-1 assays. The levels of CEBPB mRNA and protein, which may act as an antagonist of CEBPA, were found to be higher (1.4-2 fold) in PLCRF5 cells compared to HepG2 and Hep3B cells. Co-transfection of PLCPRF5 cells with siRNAs to CEBPB and CEBPA51 saRNA led to downregulation of CEBPB and senstized the PLCPRF5 cells to growth inhibition by CEBPA51. Administration of CEBPA51 complexed to either dendrimers or encapsulated in SMARTCLES nanoparticle at doses of 3-4mg/kg i.v. over 2 weeks led to a significant elevation of CEBPA mRNA in the liver. This was accompanied by a reduction (80-90%) in the size of DEN induced liver tumour nodules compared to a control oligonucleotide using both delivery vehicles. The antitumor effects following treatment with CEBPA51 using both delivery vehicles were also accompanied by reduction in markers of liver injury (bilirubin, ALT and AST). These studies support an important role for CEBPA in suppressing progression of HCC. Activation of the CEBPα gene by saRNA leading to restoration of CEBPA levels in the liver represents a promising novel approach for inhibiting the growth of HCC whilst improving normal liver function. The SMARTCLES formulation, MTL-CEBPA, was chosen for clinical development and is currently in a Phase 1 trial in patients with liver cancer (NCT02716012). Citation Format: Nagy Habib, Vikash Reebye, Xiaoyang Zhao, Jon Voutila, Robert Habib, Pål Sætrom, Hans Huber, Kai-Wen Huang, John J. Rossi, David C. Blakey. MTL-CEBPA activates the transcription factor CEBPalpha leading to inhibition of hepatocellular cancer growth [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1508. doi:10.1158/1538-7445.AM2017-1508